【作者】 梅策香；

【导师】 魏炳波；

【作者基本信息】 西北工业大学 ， 材料物理与化学， 2006， 硕士

【摘要】 三元共晶合金的快速凝固规律研究是材料科学领域的重要课题。本文分别采用熔融玻璃净化法、落管无容器处理技术和单辊实验装置系统研究了三元Ag-Cu-Ge共晶合金的凝固组织特征和相组成，揭示了三元共晶合金在深过冷和急冷条件下的快速凝固机制和晶体生长规律。 熔融玻璃净化实验中，三元Ag_38.5Cu_33.4Ge_28.1共晶合金获得了175K（0.22T_E）的最大过冷度。在0～175K过冷度范围内，凝固组织均由固溶体（Ag）、半导体（Ge）和金属间化合物η（Cu₃Ge）三相组成。小过冷条件下，三个共晶相协同生长，呈不规则层片状。过冷度较大时，共晶组织明显细化。当ΔT＞80K时，（Ge）相分离生长，（Ag）与η相呈二相层片共晶方式共生生长。初生（Ge）相的生长形态随过冷度的增大，由小面相块状向小面相枝晶转变。部分小面相（Ge）枝晶分枝生长，呈现花状。理论计算和实验结果均表明，（Ge）相领先形核。 实验研究了三元Ag_38.5Cu_33.4Ge_28.1合金的落管无容器快速凝固规律，获得最大过冷度为200K（0.25T_E）。小过冷条件下，合金的凝固组织由初生（Ge）相、（Ag）+η两相共晶和（Ge）+（Ag）+η不规则三元层片共晶组成，当过冷度超过200K时，初生相和两相共晶消失，三元共晶组织明显细化。大过冷条件下出现了球状共晶团。（Ge）相生长形态随着合金过冷度的变化表明，其生长方式随过冷度的增大，由小面相生长转变为非小面相生长。 本文还进行了三元Ag_38.5Cu_33.4Ge_28.1共晶合金的单辊急冷实验，获得厚17.5μm的薄带。XRD分析表明，合金薄带的凝固组织由（Ag）、（Ge）、η和亚稳相Ag_8.7Ge_1.3四相组成。合金凝固组织由均匀的微小晶粒组成。熔池温度场的理论计算表明，大的熔体冷却速率是形成亚稳相Ag_8.7Ge_1.3和凝固组织中晶粒细化的主要原因。 选用熔融玻璃净化装置和落管实验分别进行了三元Ag₃₄Cu₄₀Ge₂₆合金的深过冷快速凝固研究。熔融玻璃实验中，合金的凝固组织由初生η（Cu₃Ge）相和更多还原

【Abstract】 Rapid solidification of ternary eutectic alloys is an important research subject in the field of materials science. The rapid solidification of Ag-Cu-Ge ternary eutectic alloys was accomplished respectively by glass fluxing, drop tube and melt spinning method. The thesis has performed detailed investigations on phase constitution and characteristics of solidified microstructure under above conditions, which can reveal the mechanism of rapid solidification and crystal growth.By using glass fluxing equipment, the liquid Ag_38.5Cu_33.4Ge_28.1 ternary eutectic alloy was undercooled by a great degree up to 175 K（0.227_e）. X-ray diffraction analysis reveals that its microstructure is composed of （Ag） solid solution phase, （Ge） semiconducting phase and η（Cu₃Ge） intermetallic compound phase in different undercoolings. With the increase of undercooling, there occurs a transition from the cooperative growth of three eutectic phases to the （Ge） phase separates from （Ag）+η two-phase eutectic. When the undercooling exceeds 80 K, the structural morphology of primary （Ge） phase transfers from faceted blocks into branched dendrites. Some （Ge） dendrites look like flowers. Both theoretical analysis and experimental results indicate that （Ge） phase is the primary phase.Rapid solidification of Ag_38.5Cu_33.4Ge_28.1 ternary eutectic alloy during containerless conditions is studied in experiment, and the maximum supercooling is up to 200 K（0.257_l）. The results present that the rapid solidification microstructure consists of （Ge） primary phase, （Ag）+η two-phase irregular lamellar eutectic and （Ge）+（Ag）+η ternary irregular lamellar eutectic. When the undercooling exceeds 200 K, the primary phase and pseudobinary eutectic disappear, and microstructure refinement of ternary eutectic occurs. A kind of spherical anomalous ternary grains appears in deep undercooling conditions. The differences in morphology of （Ge） phase imply a transition from faceted growth to non-faceted growth with increasing undercooling.AG_38.5Cu_33.4Ge_28.1 eutectic alloy ribbon with a thick of 17.5 μm is obtained by melt spinning method. The rapid solidified microstructure is proved to be composed更多还原